1. Field of the Invention
The present invention related generally to the shaker tables to which manufactured devices are mounted for vibrational testing. More particularly, the present invention relates to a specific mounting table and to the adjustable supports for positioning the mounting table in a chamber.
2. Description of the Prior Art
Sheer tables for testing the reliability of manufactured devices are well known. Such sheer tables are used either under laboratory conditions or in conjunction with an assembly line. Often, sheer tables are mounted within thermal chambers, which gives the added flexibility of testing for defects in the manufactured product which may be exposed by elevated temperature or temperature cycling.
The sheer tables typically include a platform or mounting table upon which a device to be tested is mounted. Exciters or vibrators are attached to the mounting table to vibrate the device. It is necessary to provide an even distribution of the vibration amplitude, magnitude, direction and frequency in a range. Typical of such arrangements is U.S. Pat. No. 4,735,089 issued to Richard L. Baker, et al. That patent and others attempt to establish a uniform amplitude to the mounting table from the exciters over the range of frequencies generated.
The Baker patent identifies a problem with rigid shaker tables in achieving the objective of creating random vibration of substantially equal amplitude over the range of frequencies in a multi-axial direction. Baker does so by use of a flexible shaker table that is said to resolve potential resonance problems normally inherent in rigid mounting tables. The end result of this multi-axial excitation is a relatively complex mounting table or platform, having multiple layers, multiple connectors and multiple potential wear points.
Shaker tables can also be used in conjunction with thermal chambers to test devices for structural integrity and quality in different thermal environments or temperatures. Existing screening techniques utilize temperature cycling within a thermal chamber that can also be equipped with a vibrating mount, such as a shaker table, in the thermal chamber for shaking or vibrating the device being tested or screened. The chamber itself and the vibrating mount act as thermal loads on the chamber, thus requiring not only the energy necessary to heat and cool the device being tested during the thermal cycles, but also the additional energy required to heat and cool the chamber and the vibrating mount through those thermal cycles. Both the vibrating mount and the thermal loads react to temperature changes, radiating and/or absorbing thermal energy in response to changes in ambient temperature. Accordingly, changing the temperature of the chamber and the vibrating mount, along with the device being tested, naturally requires more energy than if the device alone were to be cycled through temperature changes. In some cases, the chamber and vibrating mount consume the majority of the energy costs to no useful end. Additionally, cycling the chamber and vibrating mount through various temperature changes requires more time than if just the device were to be cycled by itself through those temperature changes.